1. Field of the Invention
The present invention relates to an abrasive tape suitably applicable to finishing of surfaces, end faces, and so on of precision components such as optical connector ferrules, semiconductor wafers, metals, ceramics, color filters (for liquid crystal display or the like), plasma displays, optical lenses, substrates of magnetic disk or optical disk, magnetic heads, and optical reading heads, a process for producing it, and a coating agent for abrasive tape.
2. Related Background Art
The precision in grinding for finishing affects the quality of the precision components such as the optical connector ferrules and the semiconductor wafers, and grinding called mechanical polishing has been and is employed for finish grinding.
The mechanical polishing is carried out as follows. First, abrasive particles having particle diameters of 5 to 300 m.mu. are suspended in an alkaline solution such as caustic soda, ammonia, or ethanolamine to prepare an abrasive solution consisting of a colloidal solution of pH 9 to 12. While this abrasive solution is next supplied onto an abrasive cloth comprised of a resin sheet, for example a polyurethane sheet, a precision component such as the optical connector ferrule or the semiconductor wafer is ground on the abrasive cloth.
The above mechanical polishing using the abrasive solution and abrasive cloth has the following problems.
Changes will occur in the concentration of abrasive particles in the abrasive solution during grinding and in the particle size distribution of abrasive particles due to cohesion of abrasive particles, which could result in forming grinding scars or grinding spots on the ground body such as the optical connector ferrule or the semiconductor wafer. The mechanical polishing needs a process for washing the abrasive particles adhering to the surface of the ground body such as the optical connector ferrule or the semiconductor wafer away after completion of grinding, which makes the polishing step complex.
Against it, there is an idea to produce an abrasive tape obtained by applying a coating agent in which the abrasive particles are dispersed in a binder resin solution, onto a base for abrasive tape made of a plastic film and drying it to form an abrasive layer. The optical connector ferrules and semiconductor wafers, etc. are ground on this abrasive tape, but it cannot be used as an abrasive tape for finishing, because it is difficult in producing the abrasive tape to keep the abrasive particles of the particle diameters of 1 or less .mu. uniformly dispersed in the binder resin solution.
Namely, the high precision grinding for finishing is grinding with fine abrasive particles, but with a decrease in the particle diameters of abrasive particles it becomes difficult to uniformly disperse the fine abrasive particles in the binder because cohesion becomes likely to occur because of an increase in surface energy.
When the abrasive layer is formed from the coating agent containing the abrasive particles in a cohesive state, coarse particles of 5 to 10.mu. are produced in the abrasive layer, which unavoidably form grinding scars on the surface of the ground body.